In VLIW DFAPacketizer, what dose canReserveResources and ReserveResources do?

LLVM Project
1

Below is canReserveResources and ReserveResources 's code, I do not get what kind of resource it tries to reserve, and where should I define the resource.

bool DFAPacketizer::canReserveResources(const MCInstrDesc *MID) {
  unsigned Action = ItinActions[MID->getSchedClass()];
  if (MID->getSchedClass() == 0 || Action == 0)
    return false;
  return A.canAdd(Action);
}

// Reserve the resources occupied by a MCInstrDesc and change the current
// state to reflect that change.
void DFAPacketizer::reserveResources(const MCInstrDesc *MID) {
  unsigned Action = ItinActions[MID->getSchedClass()];
  if (MID->getSchedClass() == 0 || Action == 0)
    return;
  A.add(Action);
}